repack_mesh_uvs

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare destructiveHint=true, readOnlyHint=false and idempotentHint=false, but the description adds genuinely new behavioral detail: 'No undo entry, nothing saved', the pre-flight error check before any change, and the semantics of the repacked flag on success vs engine error. These are real behavioral traits not derivable from the annotations and they are internally consistent with them.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the action, followed by precondition and outcome cases, then a Returns line. Each sentence carries information, though the third and fourth sentences are dense and slightly hard to parse. Minimal waste overall.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description helpfully provides the return shape (actor_name, uv_channel, num_uv_islands, repacked, note, etc.) plus error and no-op conditions and the no-undo/no-save caveat. This is close to complete for an agent to call it correctly; only the routing-to-alternative case is thin.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents actor_name, uv_channel, target_image_width and optimize_island_rotation. The description implies the channel concept but adds no syntax or format detail beyond what the schema provides, so the baseline of 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb ('Pack') and resource ('existing UV islands on a UV channel') and destination ('standard UV space'), which cleanly distinguishes it from siblings like generate_mesh_uvs, auto_generate_mesh_uvs, recompute_mesh_uvs, and the rotate/scale/translate_mesh_uvs family. 'Existing' makes clear it operates on islands already present rather than creating UVs.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description lays out preconditions clearly (channel must exist, mesh must not be empty, channel must have UVs set) and states the success/failure outcomes for each, which is useful context. However, it never names an alternative or says explicitly when to reach for this tool versus generating UVs first (e.g. generate_mesh_uvs). Usage is implied through the precondition narrative rather than routed.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.